Difference between revisions of "1951 AHSME Problems/Problem 2"

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== Problem ==
 
== Problem ==
The [[percent]] that <math>M</math> is greater than <math>N</math>, is:
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A rectangular field is half as wide as it is long and is completely enclosed by <math>x</math> yards of fencing. The area in terms of <math>x</math> is:
  
<math> \mathrm{(A) \ } \frac {100(M - N)}{M} \qquad \mathrm{(B) \ } \frac {100(M - N)}{N} \qquad \mathrm{(C) \ } \frac {M - N}{N} \qquad \mathrm{(D) \ } \frac {M - N}{M} \qquad \mathrm{(E) \ } \frac {100(M + N)}{N} </math>
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<math>(\mathrm{A})\ \frac{x^2}2 \qquad (\mathrm{B})\ 2x^2 \qquad (\mathrm{C})\ \frac{2x^2}9 \qquad (\mathrm{D})\ \frac{x^2}{18} \qquad (\mathrm{E})\ \frac{x^2}{72}</math>
  
 
== Solution ==
 
== Solution ==
By definition of a percent, the answer is <math>\mathrm{(B)}</math>.
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Let <math>w</math> be the width. Then <math>l = 2w</math>, and the perimeter is <math>x = 2(2w)+2w = 6w \implies w = \frac{x}6</math>. The area is <math>wl = w(2w) = 2w^2 = 2\left(\frac{x^2}{36}\right) = \frac{x^2}{18}</math>, so the answer is <math>\mathrm{D}</math>.
  
== See also ==
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== See Also ==
{{AHSME box|year=1951|num-b=1|num-a=3}}  
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{{AHSME 50p box|year=1951|num-b=1|num-a=3}}  
  
 
[[Category:Introductory Algebra Problems]]
 
[[Category:Introductory Algebra Problems]]
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{{MAA Notice}}

Latest revision as of 11:19, 5 July 2013

Problem

A rectangular field is half as wide as it is long and is completely enclosed by $x$ yards of fencing. The area in terms of $x$ is:

$(\mathrm{A})\ \frac{x^2}2 \qquad (\mathrm{B})\ 2x^2 \qquad (\mathrm{C})\ \frac{2x^2}9 \qquad (\mathrm{D})\ \frac{x^2}{18} \qquad (\mathrm{E})\ \frac{x^2}{72}$

Solution

Let $w$ be the width. Then $l = 2w$, and the perimeter is $x = 2(2w)+2w = 6w \implies w = \frac{x}6$. The area is $wl = w(2w) = 2w^2 = 2\left(\frac{x^2}{36}\right) = \frac{x^2}{18}$, so the answer is $\mathrm{D}$.

See Also

1951 AHSC (ProblemsAnswer KeyResources)
Preceded by
Problem 1
Followed by
Problem 3
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All AHSME Problems and Solutions

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